In recent years, mobile users are fast increased. In order to meet great demand of the users on wireless wideband service, International Telecommunication Union (ITU) begins next generation of IMT-Advanced or standardization work of the fourth generation mobile communication system. LTF-Advanced standard will be submitted to ITU as a candidate technological standard of the IMT-Advanced system. Along with evolution of LTE (Long Term Evolution) and continuous growth of the mobile wireless communication system, higher data transmission rate and spectrum efficiency are required. Therefore, 3GPP puts forwards a Camer Aggregation (CA) technology in the new LTE-Advanced standard, which is configured to allow operators to acquire larger bandwidth for system and network deployment through aggregation of some small continuous or noncontinuous carrier waves by realizing a high speed transmission CA technology with sufficient spectrum bandwidth (up to 100 Mhz) and provide backward compatibility for prior users. However, extremely limited spectrum resource in the LTE system hardly meets the high speed transmission demand. Hence, adoption of other authorized spectrums as extension of the existing LTE authorized spectrum becomes one of considerable solutions of the LTE system.
An ASA mechanism is an improved spectrum use mechanism based on a cognitive radio technology, can ensure use QoS (Quality of Service) of the mobile authorized user in an authorized frequency band, and provides ASA spectrum service with insufficient spectrum efficiency for secondary ASA users in the case of not interfering existing users.
In prior art, an ASA-assisted TD-LTE (Time Division Long Term Evolution) system structure is as shown in FIG. 1. Known from the figure, in a scene with coexisting of the ASA assistance-based TD-LTE network and a TDD primary user network, a macro base station controls a Macro User Equipment (MUE), and a relay, and a Relay User Equipment (RUE) is connected with the relay and is positioned at the margin of a cell. In a primary user system, a primary user is controlled by a primary base station. A secondary system operator network Operation, Administration and Maintenance (OAM) and the primary base station are both connected with an ASA controller managing an ASA spectrum. The ASA controller is independent from a 3GPP system. The ASA controller only provides spectrum-related information and actual wireless resource is still in charge of the 3GP system. Two usable carrier frequencies are assumed to exist, one is an existing LTE carrier frequency f0 and the other is an ASA carrier frequency f1. The macro base station uses the carrier frequency f0 as a central frequency point of a Primary Cell (Pcell) to provide system information and basic Radin Resource Control (RRC) signaling, so as to provide low speed/high reliability data transmission for User Equipment (UE). Meanwhile, the macro base station aggregates the ASA carrier frequency f1 as a central frequency point of a Secondary Cell (Scell) to provide massive high-speed data transmission. In this scene, due to dynamics of the ASA spectrum, it is required to further research, keep and improve service continuity, QoS, interference coordination, load balance and switching mechanism of the current system.
A protection region is a specific region defined for protecting communication of the primary user. Threshold is a maximal interference threshold allowed by correct signal receiving of the primary user in the protection region. ThresholdSINR is a minimal Signal to Interference plus Noise Ratio (SINR) value. As shown in FIG. 2, C is set as a downlink signal of the primary user, I is set as an interference signal, N is set as a noise signal, then SINR of the primary user in the protection region is equal to C-I-N, which should be higher than ThresholdSINR. According to related parameters such as Threshold1, or ThresholdSINR, sending power, path loss, position information and the like, OAM (Operation Administration and Maintenance) judges and ensures that the base station or a terminal does no influence communication of the primary user when the ASA frequency point works.
In a scene with coexisting of the ASA assistance-based TDD-LTE network and TDD primary user network, relay node enhancing cell coverage are deployed on the ASA carrier frequency, the RUE connected with the relay node is positioned at the cell margin, and the primary user is positioned at the margin of the protection region. When the primary user requests for use of the ASA carrier frequency, uplink of the RUE generates interference to downlink of the primary user. Similarly, uplink of the primary user generates interference to the downlink of the RUE.
An interference scene is as shown in FIG. 3, the scene is assumed as follows:
N is set as a noise signal, I1 is interference of RUE uplink to the primary user, I2 is interference of primary user uplink to the RUE, I3 is interference of the relay to the primary user, D1 is a downlink signal of a relay access network, D2 is a downlink signal of the primary user, U1 is an uplink signal of the relay access network, and U2 is an uplink signal of the primary user.
When D2−I1−N is smaller than ThresholdSINR, the access network uplink of the relay (U1) generates interference to the downlink of the primary user (D2);
when D1−I2−N is smaller than ThresholdSINR, uplink of the primary user (U2) generates interference to the access network downlink (D1) of the relay;
when D2−I3−N is larger than ThresholdSINR, access network downlink of the relay (D1) will not generate interference to the downlink of the primary user (D2).
Under the ASA assistance-based TD-LTE network structure, the ASA carrier frequency f1 is assumed to have one or more relay nodes. When the primary user positioned at the margin of the TD-LTE cell requests for use of the carrier frequency f1 at a specific region (namely, the protection region), an RUE communication range close to the primary user is partially overlapped with the protection region, so that the RUE will generate interference to the downlink of the primary user. How to timely find and estimate interference is a key critical problem of ensuring QoS of the primary user.
Generally speaking, the most direct method is that the ASA controller informs the OAM Operator of the newest ASA spectrum use region, the OAM Operator informs the MME of reducing coverage of the macro base station at the margin of the protection region. If in the secondary cell using the ASA carrier frequency, UE or relay node exist outside the new coverage, the UE or the relay node need to be switched to the primary cell f0 unconditionally, thus severely affecting the experience and QoS of a user terminal, and causing network performance reduction; in addition, massive signalings are also consumed due to switching of massive nodes. Along with increment of user number and improvement of user requirements, the operators do not want the unconditional large batch switching.